Billie Joe Armstrong of Green Day smashes his guitar as he performs onstage during the 2012 iHeartRadio Music Festival.Credit: hristopher Polk/Getty Images for Clear Channel

Although concertgoers were quick to write off Billie Joe Armstrong's iHeart Radio festival outburst as rude, but typical, rock-and-roll antics, Us Weekly has learned there was something much more serious behind it.

At the Clear Channel-hosted event in Las Vegas Saturday afternoon, the Green Day frontman, 40, had a meltdown when show producers turned on a "one minute" sign, indicating the group had to begin wrapping up their set.

Added the singer, "I'm not f---ing Justin Bieber, you motherf---ers. Let me show you what one f---ing minute means." Armstrong then proceeded to smash his guitar, give the audience the middle finger, and storm off stage.

The neck of Green Day frontman Billie Joe Armstrong's guitar is seen after he threw it across the stage during the 2012 iHeartRadio Music Festival.Credit: Christopher Polk/Getty Images for Clear Channel

Following the outburst, a rep for the band tells Us Armstrong has decided to address his issues with substance abuse.

"Green Day's Billie Joe Armstrong is seeking treatment for substance abuse," their rep said in a statement Sunday. "Green Day would like everyone to know that their set was not cut short by Clear Channel and to apologize to those they offended at the iHeart Radio Festival in Las Vegas."

In April, Green Day announced plans to roll out an album trilogy between September 2012 and January 2013, a series of records called Uno, Dos and Tre. The band had been gearing up to promote their new tunes, but now "must regretfully postpone some of their upcoming promotional appearances," their spokesperson adds.